Fluctuation of femtosecond X-ray pulses generated by a laser-Compton scheme

A short pulse X-ray generation experiment was performed by laser-Compton scattering through interaction between a 3 ps, 14 MeV electron beam and 100 fs, 85 mJ laser photons in a 90degrees scattering configuration. The observed X-ray intensity was typically 30,000 photons/pulse and roughly matched the theoretically expected intensity. The X-ray energy and pulse duration were estimated theoretically to be 2.3 keV and 280 fs from the observed electron and laser beam parameters. The pulse to pulse fluctuation of the Xray output was measured as 25% (rms) during 30-minute operation. The fluctuation was expressed as a function of the fluctuation of the timing between the electron and laser beams. The measured fluctuation of the X-rays was approximately consistent with that caused by the fluctuation of each beam. We are improving the system to achieve the photon energy to 15 keV and the intensity to 10 million photons/pulse by increasing the electron beam energy to 40 MeV and the laser pulse energy to I J/pulse, and to stabilize the X-ray intensity to be better than 3% by improving the timing fluctuation between beams to be less than 300 fs. The amplitude fluctuation of each electron and laser beams are improved to be less than 1% to contribute to the achievement of the targeted 3% X-ray fluctuation.